The present invention relates inter alia to non-human animals and cells that are engineered to contain exogenous DNA, such as human immunoglobulin gene DNA, their use in medicine and the study of disease, methods for production of non-human animals and cells, and antibodies and antibody chains produced by such animals and derivatives thereof.
In order to get around the problems of humanizing antibodies a number of companies set out to generate mice with human immune systems. The strategy used was to knockout the heavy and light chain loci in ES cells and complement these genetic lesions with transgenes designed to express the human heavy and light chain genes. Although fully human antibodies could be generated, these models have several major limitations:    (i) The size of the heavy and light chain loci (each several Mb) made it impossible to introduce the entire loci into these models. As a result the transgenic lines recovered had a very limited repertoire of V-regions, most of the constant regions were missing and important distant enhancer regions were not included in the transgenes.    (ii) The very low efficiency of generating the large insert transgenic lines and the complexity and time required to cross each of these into the heavy and light chain knockout strains and make them homozygous again, restricted the number of transgenic lines which could be analysed for optimal expression.    (iii) Individual antibody affinities rarely reached those which could be obtained from intact (non-transgenic) animals.
WO2007117410 discloses chimaeric constructs for expressing chimaeric antibodies.
WO2010039900 discloses knock in cells and mammals having a genome encoding chimaeric antibodies.
The present invention provides, inter alia, a process for the generation in non-human mammals of antibodies that comprise a human Ig variable region, and further provides non-human animal models for the generation of such antibodies.